1. Field of the Invention
The present invention pertains to a device to convey parts to be processed towards one or more processing stations and to remove them from there.
2. Description of the Prior Art
The problem of conveying parts towards a processing station and removing them is not a new one, and even the term "conveyor-line work" is derived from devices designed to carry out these operations.
The parts are generally conveyed by trolleys or various supports, which follow a closed circuit that passes by a loading station, a processing station and an unloading station. The trolleys or supports may run on the ground or may be borne by continuous rails or taken along by a series of successive means of conveyance.
The development of automatic processing methods, and the need to obtain ever faster working rates and improved precision levels have resulted in changes in many directions. Thus, it has been seen that the most efficient results are obtained when the supporting trolleys are guided with precision at least from the loading station onwards up to and including the unloading station and when they succeed one another, each being supported on the preceding one, with the parts being fixed to the supporting trolleys so as to receive the intended processing without being shifted. As a result, in this manner, the utmost possible limit is placed on the idle time corresponding to the necessary adjustment of the processing tool to each part to be processed.
There is a system available in the market that is geared to these concerns. This system includes a series of supporting trolleys mounted on the links of an endless chain. On that part of the closed circuit comprising the loading, processing and unloading stations, rectilinear rails are provided to ensure the precise positioning, in the directions crosswise to the movement, of the supporting trolleys that run on these rails. Furthermore, the dimensions of the links of the chains and the length of the supporting trolleys are designed so that, in this rectilinear portion of the path, each of the supporting trolleys is in contact with the preceding one.
However, this useful device reaches its limits when the speeds and precision values have to be increased. The cause of this lies chiefly in the many instances of backlash or clearance that result from the use of a chain and which lead to wearing out and lack of precision in the relative longitudinal position of the supporting trolleys. Furthermore, the friction inherent in the system calls for powerful driving means which consequently have an appreciable degree of inertia that is troublesome when it is desired to have fast work-rates with non-continuous motions.